Electromagnetic ion cyclotron (EMIC) waves have long been considered major plasma waves that can cause the atmospheric precipitation of electrons. In this work, we perform test particle calculations of the interactions between relativistic electrons and EMIC waves with oblique wave normal angle (WNA) and noncircular polarization. We demonstrate advective and diffusive changes in electron pitch angle (PA) under a uniform background magnetic field for broad ranges of kinetic energy (KE), PA, WNA, and ellipticity. First, we find that the direction of advective PA changes can be of either sign, being positive (negative) for a lower (higher) initial PA. Second, an oblique WNA can enhance the advection effects on PA changes, particularly for KE ~2.5–4 MeV and a broad range of initial PAs. In contrast, a more linear polarization can decrease advection for a broad range of KE and initial PAs. Third, phase space trajectories depend strongly on specific values of WNA, ellipticity, KE, and PA. Sometimes a phase‐averaged PA change is a net result of a time‐dependent mixture of the phase trapping, untrapping, and bunching effects. Lastly, the overall effect of finite WNA and ellipticity on diffusive PA changes is less systematic than on advection. Nevertheless, we identify a range of KE and PA where the diffusion tends to increase for a larger WNA and decrease for a more linear polarization. The results in this work emphasize a strong necessity for incorporating precise information on WNA and ellipticity into evaluations of electron scattering by EMIC waves.

The preferential heating of protons in the perpendicular direction with respect to the ambient magnetic field is a well-known phenomenon in the solar corona. One of the physical mechanisms proposed to explain such a feature is the nonresonant wave–particle interaction between protons and kinetic Alfvén waves. The present paper examines this mechanism by employing a novel analytical method based upon the Hamiltonian dynamical test particle approach. The analytical nature of the present method reveals an interesting fact that the pure inductive component of parallel electric field associated with the kinetic Alfvén wave in the limit T_i/T_e ≪ 1 has little contribution. The parallel and perpendicular diffusion of protons by kinetic Alfvén waves is investigated through computing the autocorrelation function. The calculations unambiguously demonstrate that the proton heating is achieved mainly by nonresonant wave–particle interaction involving the wave magnetic field, and that the effects of the parallel electric field are minimal. It is also found that the perpendicular diffusion is orders of magnitude stronger than parallel diffusion, implying effective perpendicular heating.

This paper presents the derivation of a general wave dispersion relation for warm magnetized plasma under the two-fluid formalism. The discussion is quite general except for the assumption of low frequency and slow phase speed, for which the displacement current is negligible, under the implicit assumption that the plasma is sufficiently dense to satisfy the condition ωpe>ωce, where ωpe and ωce denote the plasma oscillation frequency and electron gyro frequency, respectively. The present discussion does not invoke charge neutrality associated with the fluctuations although it is implicitly satisfied. The resulting dispersion relation that includes the fluid thermal effects shows that there are three eigen modes, which include those corresponding to ideal MHD, namely, fast, slow, and kinetic Alfvén waves, as well as higher-frequency modes including the ion and electron cyclotron and lower-hybrid resonances. The fluid effects in the ideal MHD wave branches are influenced by the finite Larmor radius scales, and when the wave number in the cross field direction is comparable to these values, the fluid effects become significant. It is found that the Larmor radius should be interpreted in the sense as ion-acoustic gyro-radius instead of ion thermal gyro radius only. That is, it is found that the electrons also contribute to the non-ideal effect associated with the kinetic Alfvén wave. A comprehensive explanation of the polarization of each mode is also presented. The present findings indicate that the polarity may change its sign only for the kinetic Alfvén mode branch and that such a transition is based on the propagation angle. When such a change does take place, it is found that the kinetic Alfvén wave transits to an ion-acoustic mode. For each branch, it is also found that the electric field along the ambient magnetic field is purely transverse.

The Ionospheric Anomaly Monitoring by Magnetometer And Plasma-probe (IAMMAP) is one of the scientific instruments for the Compact Advanced Satellite 500-3 (CAS 500-3) which is planned to be launched by Korean Space Launch Vehicle in 2024. The main scientific objective of IAMMAP is to understand the complicated correlation between the equatorial electro-jet (EEJ) and the equatorial ionization anomaly (EIA) which play important roles in the dynamics of the ionospheric plasma in the dayside equator region. IAMMAP consists of an impedance probe (IP) for precise plasma measurement and magnetometers for EEJ current estimation. The designated sun-synchronous orbit along the quasi-meridional plane makes the instrument suitable for studying the EIA and EEJ. The newly-devised IP is expected to obtain the electron density of the ionosphere with unprecedented precision by measuring the upper-hybrid frequency (fUHR) of the ionospheric plasma, which is not affected by the satellite geometry, the spacecraft potential, or contamination unlike conventional Langmuir probes. A set of temperaturetolerant precision fluxgate magnetometers, called Adaptive In-phase MAGnetometer, is employed also for studying the complicated current system in the ionosphere and magnetosphere, which is particularly related with the EEJ caused by the potential difference along the zonal direction.

This paper investigates nonlinear evolutions of large amplitude oblique whistler waves (LOWWs) and the interaction with electrons using one-dimensional electromagnetic kinetic simulations. The present research is motivated by recent studies about the nonlinear phenomena of LOWWs. When the propagation angle is not close to the resonance cone angle, the trapping of electrons in the electric potential of LOWWs leads to a moderate damping and a mild acceleration of the electrons via the O'Neil-type damping. In contrast, when the propagation angle of LOWWs is close to the resonance cone angle, the LOWWs undergo a heavy damping accompanied by the stochastic thermalization of the electrons, especially in the perpendicular direction. It is found that the stochastic parameter S, defined by $\mathrm{S}=16k_{\parallel }^2\left(\frac{e}{m_e}\right){\Phi }_0\hspace{0.17em}\frac{\left|J_0(k_{\perp }\rho )\right|}{{\omega }_{ce}^2}$ , is a crucial factor determining the damping process. This result demonstrates the importance of self-consistent electron kinetic effects, which are not included in the previous single-particle or fluid approach. The implications of the present findings are discussed.

Ionospheric Anomaly Monitoring by Magnetometer And Plasma-probe (IAMMAP) is a suite of scientific instruments used in the Compact Advanced Satellite 500-3 (CAS 500-3), which is planned to be launched by the KSLV (Korean Space Launch Vehicle) in 2025. The main scientific objective of IAMMAP is to understand the complicated correlation between the equatorial electrojet (EEJ) and the equatorial ionization anomaly (EIA), both of which play important roles in the dynamics of ionospheric plasma in the dayside equator region. The magnetic field generated by the EEJ is tiny (~several nT) compared to the background geomagnetic field (~30,000 nT); thus, a high-resolution magnetometer with a wide dynamic range is required to investigate its correlation with the EIA. To achieve this required resolution, IAMMAP includes a set of improved fluxgate magnetometers named the AIMAG (Adaptive In-phase MAGnetometer), which was developed by adopting new technologies. Here, we report the analysis results of the manufactured AIMAG performance based on trade-off studies for optimizing the circuit and sensor configurations. The results support that the AIMAG sensor and electronic circuits with new concepts and technologies will lead to successful observations of EEJ signatures in the ionosphere.